Optical systems for measuring form and geometric dimensions of precision engineered parts

A method for determining a geometric property of a test object, the method comprising:

• interferometrically profiling a first surface of the test object with respect to a first datum surface;
• interferometrically profiling a second surface of the test object with respect to a second datum surface different from the first datum surface;
• determining a spatial relationship between the first and second datum surfaces;
• and
• calculating the geometric property based on the interferometrically profiled surfaces and the spatial relationship between the first and second datum surface,
• wherein the determining of the spatial relationship comprises:
• interferometrically profiling a first surface of a initialization artifact with respect to the first datum surface;
• interferometrically profiling a second surface of the initialization artifact with respect to the second datum surface;
• calculating an initial spatial relationship between the first and second datum surfaces based on at least the profiled surfaces of the initialization artifact;
• and
• adjusting the first and second datum surfaces to accommodate the first and second surfaces of the test object,
• wherein the first and second surfaces of the initialization artifact are the front and back of a common interface.

An apparatus for determining a geometric property of a test object, the apparatus comprising:

• an interferometric profiling system which during operation interferometrically profiles a first surface of the test object with respect to a first datum surface and interferometrically profiles a second surface of the test object with respect to a second datum surface different from the first datum surface;
• and
• an electronic processor coupled to the interferometric profiling system, wherein during operation the electronic processor calculates the geometric property based on the interferometrically profiled surfaces and a spatial relationship between the first and second datum surfaces;
• and
• a displacement measuring interferometer positioned to measure the spatial relationship between the first and second datum surfaces.

An apparatus for determining a geometric property of a test object, the apparatus comprising:

• an interferometric profiling system which during operation interferometrically profiles a first surface of the test object with respect to a first datum surface and interferometrically profiles a second surface of the test object with respect to a second datum surface different from the first datum surface;
• and
• an electronic processor coupled to the interferometric profiling system, wherein during operation the electronic processor calculates the geometric based on the interferometrically profiled surfaces and a spatial relationship between the first and second datum surfaces,
• wherein the interferometric profiling system comprises an interferometric optical profiler having a first viewing port for viewing the first surface of the test object and a second viewing port for viewing the second surface of the test object, wherein the first and second surfaces correspond to different sides of the test object.

An apparatus for determining a geometric property of a test object, the apparatus comprising:

• an interferometric profiling system which during operation interferometrically profiles a first surface of the test object with respect to a first datum surface and interferometrically profiles a second surface of the test object with respect to a second datum surface different from the first datum surface;
• and
• an electronic processor coupled to the interferometric profiling system, wherein during operation the electronic processor calculates the geometric property based on the interferometrically profiled surfaces and a spatial relationship between the first and second datum surfaces,
• wherein the interferometric profiling system comprises an interferometric optical profiler having a first viewing port for viewing the first surface of the test object and a second viewing port for viewing the second surface of the test object, and
• wherein the optical profiler is configured to direct a first portion of EM radiation from a source towards the first viewing port, direct a second portion of the EM radiation towards the second viewing port, and direct at least one additional portion of the EM radiation within the optical profiler.

An apparatus for determining a geometric property of a test object, the apparatus comprising:

• an interferometric profiling system which during operation interferometrically profiles a first surface of the test object with respect to a first datum surface and interferometrically files a second surface the test object with respect to a second datum surface different from the first datum surface;
• and
• an electronic processor coupled to the interferometric profiling system, wherein during operation the electronic processor calculates the geometric property based on the interferometrically profiled surfaces and a spatial relationship between the first and second datum surfaces,
• wherein the interferometric profiling system comprises a first interferometric optical profiler for viewing the first surface of the test object and a second interferometric optical profiler for viewing the second surface of the test object.

An apparatus for determining a geometric property of a test object the apparatus comprising:

• an interferometric profiling system which during operation interferometrically profiles a first surface of the test object with respect to a first datum surface and interferometrically profiles a second surface of the test object with respect to a second datum surface different from the first datum surface;
• an electronic processor coupled to the interferometric profiling system, wherein during operation the electronic processor calculates the geometric property based on the interferometrically profiled surfaces and a spatial relationship between the first and second datum surfaces;
• and
• a gauge object having first and second surfaces, the first surface being positioned to be profiled by the interferometric profiling system with respect to the first datum surface and the second surface being positioned to be profiled by the interferometric profiling system with respect to the second datum surface,
• wherein the gauge object is positioned to be in a field of view of the interferometric profiling system during interferometric profiling of the test object.

An apparatus for determining a geometric property of a test object, the apparatus comprising:

• an interferometric profiling system which during operation interferometrically profiles a first surface of the test object with respect to a first datum surface and interferometrically profiles a second surface of the test object with respect to a second datum surface different from the first datum surface;
• and
• an electronic processor coupled to the interferometric profiling system, wherein during operation the electronic processor calculates the geometric property based on the interferometrically profiled surfaces and a spatial relationship between the first and second datum surfaces;
• wherein the electronic processor uses at least one value indicative of PCOR dispersion in the interferometric profiling system and the test object to calculate the geometric property.

An apparatus for determining a geometric property of a test object, the apparatus comprising:

• an interferometric profiling system which during operation interferometrically profiles a first surface of the test object with respect to a first datum surface and interferometrically profiles a second surface of the test object with respect to a second datum surface, wherein the interferometric profiling system comprises at least one movable stage for adjusting the position of the first datum surface and the second datum surface;
• a displacement measuring interferometer positioned to measure a change in a relative position of the first and second datum surface caused by an adjustment to the at least one movable stage;
• and
• an electronic processor coupled to the interferometric profiling system and the displacement measuring interferometer, wherein during operation the electronic processor calculates the geometric property based on the interferometrically profiled surfaces and the relative position of the first and second datum surfaces.

A method for determining a geometric property of a test object, the method comprising:

• interferometrically profiling a first surface of the test object with respect to a first datum surface;
• interferometrically profiling a second surface of the test object with respect to a second datum surface different from the first datum surface;
• determining a spatial relationship between the interferometrically profiled surfaces which accounts for PCOR dispersion;
• and
• calculating the geometric property based on the interferometrically profiled surfaces and the spatial relationship.

A method for determining a geometric property of a test object, the method comprising:

• interferometrically profiling a first surface of the test object with respect to a first datum surface;
• interferometrically profiling a second surface of the test object with respect to a second datum surface different from the first datum surface;
• providing a spatial relationship between the first and second datum surfaces based on at least one interferometric displacement measurement;
• and
• calculating the geometric property based on the interferometrically profiled surfaces and the spatial relationship between the first and second datum surfaces,
• wherein the first and second surfaces of the test object are interferometrically profiled from a common side and the first and second datum surfaces are spaced from one another by a distance greater than a profiling range η of an interferometry system used for the interferometric profiling steps.

An optical profiling system comprising:

• a broadband source;
• a scanning interferometer which during operation separates input light into a first wavefront and a second wavefront, directs the first wavefront along a reference path including a partially reflective first surface and a reflective second surface and the second wavefront along a measurement path contacting a measurement object, and, after the second wavefront contacts the measurement object, combines the wavefronts to produce an optical interference pattern;
• a detector producing interference data in response to the optical interference pattern;
• an electronic processor coupled to the detector for analyzing the interference data
• a scanning controller coupled to the scanning interferometer and the electronic processor, wherein during operation the scanning controller causes the scanning interferometer to adjust the position of the first and second surfaces.